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Updated on October 13, 2014
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Review of SpyderLensCal - Datacolor

The focus chart SpyderLensCal by Datacolor was created to bring a solution to a real problem on our cameras full of pixels: autofocus accuracy. Autofocus are indeed quick and accurate... but not enough because very often, the focus isn't where you would have expected it to be. The chart SpyderLensCal is here to help us set the autofocus for our pair camera body/lens accurately...

Box SpyderLensCal by DatacolorAs I explained it in details in my page dedicated to camera calibration, the autofocus on our cameras attracts more and more criticism; not that it doesn't work, but it doesn't work exactly as we'd want it to. In fact, it doesn't focus exactly where we'd expect it to! The focus is often slightly backwards or forward. It is called Front focus or Back focus.

This problem always existed but it was barely visible until our bodies got lots of pixels hence improved in accuracy. Up to 10 Mpixels, the problem often went unnoticed, especially with lenses that were not too luminous, but it became frankly annoying over 10 Mpixels. From 20 Mpixels on and with lenses opening at f2,0 or more, accurate setting is compulsory.

Engineers thus had the idea to add a menu to the settings of our bodies, called "Autofocus micro-adjustment" for some and "Accurate setting of autofocus" for others. It enables to set the autofocus for each lens and for a given body very accurately. This setting is thus specific to given pair camera body/lens.

To make it easier, Datacolor thus invented the appropriate tool: SpyderLensCal. Let's meet and see how it works...

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Presentation of Datacolor's SpyderLensCal

This chart was invented in 2010 to help us solve a more and more annoying problem; the lack of accuracy of the focus plane of our autofocus.  

The calibration kit and its box

The chart is sold folded in a box. It is made of plastic, hence robust unlike "homemade" solutions printed on a papersheet. Good news #1, it can be folded and unfolded while using it. When you don't use it or you want to carry it, it doesn't take much space. Unfolded it is about 15 cm large. Folded, it is only a few millimeters thick! 

Datacolor's SpyderLensCal

Main characteristics

  • Once implemented hence unfolded, it is made of a focusing panel (vertical);
  • a graduated reglet, tilted at 45° with very well printed lines;
  • a spirit level;
  • a Kodak 1/4" screw thread to place it on a tripod at the right height.
  • Robust enough plastic chart.


Technical specifications

 
SpyderLensCal
Average price: 65 €
Focus chart
Yes
 
Sprit level
Yes
 
Tripod fastening
Yes / Kodak 1/4" screw thread (small screw thread)
 
Tilted reglet
Yes
 
Bulkiness (folded)
13 x 22 x 0.7 cm
 
Bulkiness (unfolded)
13 x 15.5 x 15 cm
 
Weight
290 grams
Company

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Autofocus calibration step by step

The success of accurate setting of your autofocus for each of your lens depends for a good part on the right installation of the chart and the camera. You need to understand that we're measuring very, very precise things here and that you'll need a bit of rigor during this phase.

1 - Installation of the chart SpyderLensCal

Unfold the chart SpyderLensCal correctlyIt is not essential, but you'd better fasten your chart on a tripod's head to level it easily. Then unfold the reglet at 45°. The focusing panel must be perfectly perpendicular to the fastening panel. It must be unfolded as in the figure here, which is easy because it features a blocking bolt.

2 - Installation of the camera

a) After choosing the lens you want to calibrate, the camera must also be placed at the right height. In fact, the center of your lens must be placed at the same height as the autofocus focusing zone on the chart.


The camera must be at the same height as the chart SpyderLensCal


b)The camera must be perfectly horizontal. Use a spirit level.

c) Very important! Be sure to deactivate lens stabilization if it features this functionality.

d)Very important! Make sure to choose the central autofocus collimator.

e) Set diaphragm opening of your lens at the maximum aperture (wider aperture).


Spirit level - Stabilization on OFF - Maximum lens aperture

3 - How far?

What is the best distance to calibrate the accurate setting of autofocus? According to the litterature on Datacolor's website, it is recommended to place the chart at 30~50 x the focal distance of your lens. For a 50 mm, it would represent: 30~50 x 50 = 1,500 to 2,500 mm hence 1.5 to 2.5 m. But at this distance, a 50 mm f1,4 has a depth of field of at least 5 cm hence 2.5 cm forward AND backwards relatively to the focusing plane. Hard to be accurate even with this very luminous lens, imagine with a lens that would "only" open at 2.8 or 4! I thus prefer 20 x because at 50 x, it is more difficult to identify the zone of sharpness with precision.
It corresponds roughly to a situation where the camera is placed close to the infinite. But the most important is to calibrate your lens at the distance you use most frequently.

 

SIGMA Optimisation Pro - New in!

To my knowledge, only SIGMA through an original new program called Sigma Optimization Pro enables to calibrate the last lenses of the ART series.   

Sigma-optimisation-pro

This program enables to set autofocus accurately depending on the focusing distance AND, if it's a zoom lens, depending on the focal. It is the most evolved program and I think everybody will be using it shortly because our bodies have more and more pixels and big defects become real disabilities.


My recommendation! The distance will depend a lot on the depth of field of your lens. If you own a very luminous lens (f1,2 to f2,0), at about 20 - 30 x the focal distance, you'll be accurate. With less luminous lenses (f2,8 and over) the depth of field becomes such that it will be difficult to make an accurate setting without getting closer to the chart.
Make tests with your pair lens/camera body because it seems that there's no universal rule. Sigma has a very evolved program through Sigma Optimisation Pro (above) and Nikon only enables to make one setting per lens, even if it's a zoom one. The experience of colorimeters with a high number of pixels make me think that a "Sigma-like" optimization is on its way...

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Control and calibration of the autofocus

We'll now start shooting in order to set the autofocus of your camera body for a given lens accurately. We'll take the example of a Canon lens 135 mm F2,0. It is set on F2.0, its full aperture (it is thus a very luminous lens with a shallow depth of field at full aperture).

Align your camera body and the chart SpyderLensCal

Launch the autofocus by placing the central collimator on the central chartIn the viewfinder or with the Liveview, center the collimator in the right chart after checking you're only using the central collimator (zoom in as much as possible if you activate the Liveview).

First calibration test...

Alignment of the body and the chart SpyderLensCal1 - Activate autofocus (central collimator only) and focus on the small chart (just next to the zero (0). Be careful not to place the collimator on the reglet, even slightly.


2 - We are now going to check this autofocus visually: activate Liveview if your body features this functionality. Zoom in as much as you can with the magnifying glass and analyse the image. It should theoretically be sharp on the zero (0) line but it is only seldom the case... Most often, the reglet is sharp before (front focus) or after (back focus) the zero line.


3 - So if it isn't the case, try to modify the focusing point manually so that the 0 line and the autofocus chart (which are in the same plane) are now really sharp. If you get a sharper image on the zero line, it means that your autofocus isn't set perfectly. Try to see if you shifted your focus forward or backwards to know if your problem was a front focus or a back focus.

... and accurate setting of the autofocus

1 - Place the cursor of micro-adjustment of the autofocus on 0. Change your focus manually so that your chart is really blurred (and do it again every time during the whole process). Focus with the autofocus, still on the central chart. 


2
- Make a test photo. View this photo in Photoshop at 100%. The chart and the 0 line must be slightly blurred as you noticed at the previous step. Try to find where the reglet is completely sharp: in front of or behind the chart and 0 line plane.

My recommendation! The more your lens will be luminous and the closer you'll be from the chart and the easier it will be to see precisely where this point is... 


3
- Depending on whether your problem is a back or front focus, place the cursor on:

  • +5 then + 10 and finally + 15 if you have a front focus (sharp before the 0 line),
  • - 5, -10 then -15 if you have a back focus (sharp behind the 0 line).
  • Shoot three new photos.


My analysis: in the example below (Canon 135mm F2,0 on a Canon 1 DS Mark III), the autofocus is slightly forward. It is thus a front focus. The focusing point is in fact on the reglet, close to the value +1.5 cm (the depth of field zone being around 1 to 2 cm). You'll have to move the focus backwards. To save time and not take 20 photos with the cursor in the 20 possible positions, I'll start roughing out by shooting three photos with three settings: here, +5, +10 and +15 (hence backwards on the Canon).


Accurate setting of the autofocus: cursor at 0

The focus is about 1.5 centimeters forward (front focus) - Your eyelash will be sharp but not your iris!


4
- Analyze your three photos at 100% in Photoshop. In my situation, the photo at +5 is still clearly front-focused. The 0 line is still blurred but the sharp line is at about + 1 cm. On the photo at +10, the sharp line is closer to the 0 line but still slightly forward. And finally, on the photo at +15, the sharp line is this time slightly behind the 0 line.


5
- I shoot two more photos at +12, +13. After a few tests/failures, I thus find the value: +12 (backwards) as shown in the illustration below:  


Accurate setting of the autofocus: 12 backwards

Important note! The focusing plane of the chart and the 0 line are perfectly sharp now. In fact, the depth of field makes the image sharp a bit before and behind the 0 line. I know that my setting is right because the lines 1 and -1 are also blurred. Note that autofocus and Liveview are matching now. 

My recommendations! - Every time you're doing an autofocus focusing again, change the focus purposedly and manually. The autofocus must really work and start from scratch!
- Moreover, replay the sequence several times: unset focusing / refocus automatically to make sure that your average setting is right. On old lenses, the gearing thread of the USM engine is wider and the focus is less accurate. You can have the impression that the focus is made on different points repeatedly...

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Questions/Answers


Q - Special case: zoom lenses.

Canon zoom 24-70 mmA: In fact, since the Nikon D800 and its 36 Mpixels were released, we're even more careful about points that could be neglected until then. You mustn't forget that this D800 replaces the D700 which had "only"... 12 Mpixels hence 3x less!!! The autofocus might better be accurate indeed. Until now, Nikon didn't allow the accurate setting of autofocus on several zoom positions, unlike Canon or Sigma and its new program Sigma Optimisation Pro. As for the rest, the more pixels you'll have and the more micro-adjustments you'll have to make.


Q - How about manufacturing quality? Are our cameras of worse quality now?

A: I don't think so. I believe however that systematic augmentation of the number of pixels brings a lot of problems, or more precisely that our colorimeters' accuracy reaches technical limits that weren't a problem until now. Fortunately, numerous problems have technical or virtual solutions that are easy to implement. I'd rather have the manufacturers produce robust and reliable camera bodies for an affordable price, and when they can, let us take care of the optimization of certain settings like the calibration of our monitors or the micro-adjustment of autofocus.


Q - Particular case of Sigma ART lenses and their program Sigma Optimisation Pro: future reference?  

A: I don't know yet. I have the feeling that we'll be coming to it progressively with the increasement of the number of pixels in our colorimeters though. Problems that were invisible until now appear with thrice more pixels !

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Conclusion and rating!

The autofocus chart SpyderLensCal gathers all required functionalities to set the autofocus for each lens accurately. Its value for money is really very good even if a "homemade" solution, made following the same logic, would do just as well... for free. But you can use the SpyderLensCal immediately and it is robust since it is made of plastic and not of paper!
It is very convenient to install and even more to use because reading the photos is easy. You immediately see on your photos enlarged at 100% where the focusing point is.  

 

Ratings


 

SpyderLensCal

   
Manufacturing quality
5 stars
 
 
Implementation/settings
5 stars
 
 
Setting reliability
4,5 stars
 
 
Value for money
5 stars
 
 
PROS...
Excellent value for money! - Quick and reliable implementation - convenient - can be completely folded for easy storage or to carry it - wide autofocus focusing zone - clear identification of the sharpness zone.
 
 
CONS...

The manufacturing quality looks a bit "cheap" - the millimeters on the reglet don't match the settings of the cursor in the menu of any camera body.

 
 
OVERALL RATING
9.0 / 10
 


My opinion: the most convenient and "intuitive" solution on the market! Its implementation is quick, easy and the accurate setting of each lens is reliable and can be reproduced. Not free, but that's justified. Excellent value for money! 


Buy Datacolor's chart SpyderLensCal

   
Retailers
Price (€)  
   
Logo Amazon.fr
60.00
Buy this colorimeter on Amazon.fr
   
Logo Miss Numérique
58.90
Buy this colorimeter on Miss Numérique

 

 



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